Taxonomic Notes

The scientific name for the Australian variable lacewing is Drepanacra binocula (Newman, 1838), but it is sometimes misspelt with an ‘r’ added to the specific epithet so that the name reads Drepanacra binocular.

In addition to the synonyms listed above, numerous subspecies or varieties were created in the past. None of these are now accepted as valid.

Biostatus and Distribution

This adventive lacewing comes from Australia and is widespread in New Zealand. In New Zealand it is mainly found in trees and shrubs where it feeds on aphids, psyllids and whiteflies.

Conservation status: The Australian variable lacewing is widespread and not threatened.

Life Stages and Annual Cycle

Little is known about the annual cycle of the Australian variable lacewing in New Zealand. Larvae are found in colonies of prey during the summer. There are probably several generations per year. The adults hide during the day while larvae appear to remain active in colonies of prey.

The adults are brown with two pairs of brown ­wings that are held roof-like over their bodies. The wings have a distinctive ‘hook’ at their tip. The pale and dark markings on the wings are very variable and this variability is the reason for the numerous subspecies/varieties that have been described. Many of these variants are illustrated by Hudson in his 1950 book, ‘Fragments of New Zealand entomology”. The adults are about 10 mm long, have small heads with large black compound eyes and long antennae that are held out in front when they are walking or kept tucked under their body when at rest.

After mating, the female lacewing lays eggs by or in colonies of prey. The eggs may be on long thin stalks like other lacewings. A small larva hatches from the egg. As the larvae grows, it moults, getting a new larger skin. All larvae appear to look the same. They are long with a small head in front with antennae and prominent jaws. The jaws are hollow and are formed from the mandibles and maxillae that are fused and form a siphon through which the larvae suck up their food.

When the last instar (stage) larva is fully grown, it finds a sheltered place where it spins a loose cocoon. Inside This it spins another smaller cocoon in which it moults into a pupa. Legs, wings and antennae are visible on the pupa. When the adult is fully formed, it emerges and makes a hole in the cocoon. Its wings expand and harden.

Myra Carter in her 1949 paper on the Pittosporum psyllid, Trioza vitreoradiata, found that a female Australian variable lacewing could lay 182 eggs. In the laboratory, it took 27-30 days from egg to adult. During this time a larva ate about 90 psyllid nymphs. The time spent as a pupa was a little longer than time as a larva. The length of time of each life stage depends on temperature, being shorter at higher temperatures.

Walking and flyingBoth adult and larval stages of the Australian variable lacewing have three pairs of legs that can be used for walking. When the larva walks it uses the tip of the abdomen to hold onto the plant surface. Adults have wings and can fly.

FeedingBoth adults and larvae eat aphids, psyllids and whitefly. They may feed on other small insects. The jaws of the adult are used for holding and chewing the prey, which may be completely consumed. The jaws of the larva are hollow and are used to hold onto the prey and to suck up the body contents.

Recognition

The distinctive wings of the Australian variable lacewing enable adults to be easily recognised in New Zealand. The shape and brown colour give an adult at rest the appearance of a dead leaf making them difficult to find. The pale and dark markings on the adult wings are very variable. The larva is not quite as distinctive, but with a little experience can be distinguished from other lacewing larvae that are found on plants. The larvae are stouter than Tasmanian lacewing larvae and may be covered with wax from whitefly.

Natural Enemies

Only one natural enemy of the Australian variable lacewing is recorded in New Zealand.

ParasitoidMature Australian variable lacewing larvae may be parasitised by Anacharis zealandica Ashmead, 1900 (Hymenoptera: Figitidae). Several eggs of the parasitoid may be laid in a larva, but only one parasitoid larva develops in each lacewing larva. The parasitised lacewing larva spins a cocoon as normal, but instead of pupating after a few days, it stays as a larva. After about 20 days, a parasitoid larva emerges, having eaten the lacewing from the inside. The parasitoid larva has small mandibles and two rows of eight dorsal spines. The parasitoid larva usually pupates in the lacewing cocoon. It is white at first, but turns black before adult emergence. The adult Anacharis zealandica is shiny black and about 2.5 mm long.

Prey/Host

In New Zealand, the Australian variable lacewing has been recorded feeding on aphids, psyllids and whitefly. Most prey are associated with shrubs and trees, though one species, a whitefly lives on ferns.

Myra Carter in her 1949 paper on the Pittosporum psyllid, Trioza vitreoradiata, found that larvae of the Australian variable lacewing will eat eggs of its own species when kept in captivity with prey.

Information Sources

Hudson,G.V. 1950: Fragments of New Zealand entomology. - a popular account of all New Zealand cicadas. The natural history of the New Zealand glow-worm. A second supplement to the butterflies and moths of New Zealand and notes on many other native insects. FERGUSON & OSBORN LTD., WELLINGTON: 188 PP; 18 PLS. (Plate 10 has illustrations of Drepanacra binocula).

Tillyard RJ 1923 (1922). Descriptions of new species and varieties of lacewings (order Neuroptera Planipennia) from New Zealand, belonging to the families Berothidae and Hemerobiidae. Transactions and Proceedings of the New Zealand Institute 54: 217-225.

Valentine EW 1967. A list of the hosts of entomophagous insects of New Zealand. New Zealand Journal of Science 10(4): 1100-1209.

Acknowledgements

The New Zealand Institute for Plant & Food Research Limited (Plant & Food Research) for permission to use photographs.